Vertical slide bolt door lock



April 2, 1957 .L H. ROETHEL 2,787,488

VERTICAL SLIDE BOLT DOOR LOCK Filed June 30, 1954 2 Sheets-Sheet l April 2, 1957 Filed June 50, 1954 J. H. ROETHEL 2,787,488

VERTICAL SLIDE BOLT DOOR LOCK y 2 Sheets-Sheet 2 HTTa/VNEK United States Patent O 2,787,488 VERTICAL SLIDE BDLT DOOR LOCK John H. Roethel, Coral Gables, Fla., assigner to Roethel Engineering Corporation, Denoit, Mich., a corporation of Michigan Application June 3l), 1954, Serial No. 440,359 6 Claims. (Cl. 292-165) This invention relates to a latch control mechanism for swinging doors, particularly the doors of automobile or other vehicle bodies, an object of the invention being to provide an improved door latch mechanism which is characterized by its simplicity and compactness in construction and which is economical to manufacture, comparatively quiet in operation and eicient in use.

The improved door latch mechanism of the present invention comprises a substantially vertically slidable latch bolt normally urged into latching engagement with a striker or keeper device mounted on a body pillar, outer and inner manually operable means for disengaging the latch bolt from the striker or keeper device, and improved control means for selectively controlling the eiectiveness of the outer manually operable actuating means in disengaging the latch device from the striker or keeper.

More particularly the present invention comprises a support having a main plate portion and a flange portion angularly related thereto. A vertically slidable latch bolt is mounted on the front face of the main plate portion, said bolt having a toothlike portion thereof normally projecting into keeper or striker engaging position. Actuator means, preferably including a lever operable by an outer manually operable means such as a push button, is mounted on the rear or opposite side of said plate portion, said actuator means having a part thereof in opposing relation to a part of said latch bolt, one of said parts projecting through an aperture in said plate portion in said opposing relation to the other of said parts. The actuator means is constructed and arranged so that the elements thereof may be operatively disassociated thereby rendering the outer manually operable means ineffective to disengage the latch device from the striker or keeper device. Such disassociation of the actuator means elements is accomplished through actuation of a control means, such control means being actuatable from the outside of the door or from the inside of the door.

Another feature of the present invention is the provision of a means for automatically reassociating the elements of the actuating means in the event that such elements are disassociated with the vehicle door in an open position and the door is then moved to a closed position.

Further objects and features of the present invention herein illustrated will appear in the following description, reference being had to the accompanying drawings forming a part of the specification wherein like reference numerals designate corresponding parts in the several views.

Fig. 1 is a sectional view of the main plate portion of a latch mechanism constructed in accordance with the present invention, the view being taken substantially along the line 1--1 of Fig. 2 looking in the direction of the arrows.

Fig. 2 is a sectional view taken substantially along the line 2-2 of Fig. l looking in the direction of the arrows.

Fig. 3 is a side elevation of Fig. 1.

Fig. 4 is a plan view of Figs. 1 and 2 in combination.

Fig. 5 is a view in part similar to Fig. 1 illustrating the operative parts of the latch mechanism in one operative position.

2,787,488 Patented Apr. 2, 1957 ICC Fig. 6 is a view in part similar to Figs. 1 and 5 illustrating the operative parts of the latch mechanism in another operative position.

Fig. 7 illustrates the relationship of the latch bolt of the latch mechanism to a keeper or striker device.

In the drawings there is illustrated, by way of example, a particular embodiment of the present invention as applied to the doors and frame structures of an auto mobile. The illustrated embodiment of the invention comprises a case plate 10 provided with screw bosses 11 which are adapted to receive screws for fastening the case plate 10 to the jamb portion or free edge wall of the door, the case plate having a ilange 12 which is adapted to be positioned along the inner panel of the door. The case plate 10 is adapted to be mounted on the door with its longitudinal axis extending substantially in the direction of the vertical axis of the door. Secured to the front face 13 of the case plate is a substantially rectangular housing 14 having an opening 15I in lower end thereof.

The illustrated latch bolt 16 is preferably molded of a plastic material, such as nylon, which is characterized by its low coeflicient of friction when sliding on steel and which has low adhesion to ice and therefore will not readily freeze to the case plate. As illustrated, the latch bolt 16 has a cross-sectional thickness substantially equal to the distance between the case plate surface 13 and the inner face of the housing plate portion 17. The fit of the latch bolt 16 between the two plate surfaces is such that the bolt will be freely movable therebetween.

In order to lighten the latch bolt 16 and to save on the quantity of material used therein, the latch bolt is provided with a number of recesses in the side thereof adjacent the face 13 of the case plate, some of the recesses having functional utility other than merely serving to lighten the bolt. The latch bolt 16 is an elongated and vertically extending member and is provided with a toothlike projection 18 thereon extending below the lower edge 15 of the housing. The toothlike projection is adapted to engage a striker or keeper device, as illustrated in Fig. 7, the keeper being generally designated 19.

Associated with the bolt 16 is a latch bolt release or actuator means, generally designated 20. The latch bolt release means consists of several operatively associated members. The first of these members comprises a generally vertically extending lever 21 which is pivotally supported at its lower end on the inner face 22 of the case plate 10 by a shoulder stud or rivet 23. At its upper or free end 24 the lever 21 is provided with a flange 25 thereon. This flange 25 is engageable on the outer end thereof by an outside manually operable means, such as a push button 26, for imparting pivotal or swinging movement to the lever 21.

The lever 21 is normally urged in a clockwise direction, as viewed in Fig. l, by a spiral spring 27. The inner end 28 of the spring 27 is seated in a kerf or slot 29 in the shoulder stud 23. The free end 30 of the spring 27 lies in abutting relation to a lug 31 turned at a right angle to the plane of the lever 21. The case plate 1t) is also provided with a lug 32 on the outer edge thereof turned at a right angle to the plane thereof. The lug 32 is a stop limiting clockwise movement of the lever 21 when urged in such direction by the spring 27.

A multi-armed member, generally designated 33, is pivotally mounten1 at one end thereof by a pivot stud 34 on the lever 21 intermediate the ends thereof. As shown in Fig. 1, the multi-armed member 33 is provided with three generally horizontally extending arms; an upper arm 35, an intermediate arm 36, and a lower arm 37.

The intermediate arm 36 is normally operatively asi sociated with a bell crank lever, generally designated 3.8; Which `is pivoted on -the inner face 22 of the case plate by a pivot or shoulder stud 39. The bell crank 39 is provided with -two arms, one arm 46 extending at a slight angle below the horizontal from the'pivot stud 39 and the second arm 41 extending in a substantially vertical direction downwardly. The arm 4t) has mounted on the swingable end thereof a horizontally extending roller 42 adapted to project through an aperture 43 in the case plate 10 toward the latch bolt 16. The roller 42 projects through the aperture 43 into a recess portion 44 of the latch bolt 16 and underlies'the edge e5 of a wall section thereof. By virtue of this construction, the bell crank lever 38 and the latch bolt 16 are so related that if the bell crank lever is swung in a clockwise direction, as viewed in Fig. l, vthe roller 42 will abut the edge 45 of the latch bolt 16 and thereby lift the latch bolt upwardly.

It will be noted in Fig. l that the upper end of the arm 36 .of the multi-armed member 33 lies in abutting relation tothe lower end of the bell crank arm 41. Thus, upward movement of the latch bolt 16 results from the actuation of the following elements of the latch mechanism, reference being had to Fig. l: The push button 26 upon being moved tothe left causes the lever 21 to be swung in a counterclockwisc direction toward the ange 12. Such movement of the lever f2.1 results in the multiarmed member 33 being bodily shifted in a substantially horizontal direction toward the flange 12 thereby causing the upper end of the ,arm 36 thereon to abut the lower end of the arm 41 of the bell crank 38. The bell crank 38 will be swung in a clockwise direction causing the roller 42 to lift the latch bolt 16 upwardly in unlatching direction.

The latch bolt 16 is yieldingly urged toward latching direction, that is, downwardly, and the bell crank lever 38 is urged toward its normal position shown in Fig. 1 by a single cylindrical coil spring 46. The spring 46 is seated in a recess 47 in the latch bolt. At its upper end the spring 31 abuts against the underside of a lug 4S projecting into the recess 47, the lug being lanced out of the ymaterial of the face plate. The spring 46 urges the latch bolt 16 downwardly at all times, the range of downward movement being limited by the upper edge of the recess 47 abutting the lug 33. Thus, through the action of the spring on the latch bolt 16, the toothlike projection 18 on the latch bolt is adapted to be yieldingly maintained in striker or keeper device 19 engaging position.

Because of the abutting relationship of the latch bolt edge v45 with 4the roller 42 on the end of the bell crank arm 4t), the spring 46 is effective to urge the bell crank lever in a counterclockwise direction about the lever pivot axis 39. Thus, the single spring 46 is utilized to maintain the latch bolt 16 and the bell crank 38 in their normal positions.

The present latch mechanism incorporates a remote control mechanism so constructed as to permit movement of the latch bolt V16 independently of the release lever means 20. This remote control mechanism comprises a bell crank lever 4 9 preferably manually actuated through a linkage system from the inside of the door remote from the case plate by means of a door handle (not shown) mounted on the inner panel of the vehicle door. Referring particularly to Fig. 2, the bellV crank lever 49 is shown pivotally mounted on the flange 12 by means of a pivot or shoulder stud 50. The bellV crank lever 49 is provided with a substantially downwardly extending arm 51 and a substantially horizontally extending arm 52. vThe arm 51 is adapted to be connected by a draft link 53 to the remote control handle mechanism. The bell crank lever' arm 52 vis ol'r'set at its free or swingable end 54. The end 54 extends through the aperture 43 in `the case plate 10 so as to underlie an edge 55 of the latch bolt recess 44. Movement of the bell crank lever 49 in a counterclockwise direction, as viewed in Fig. 2,

4 will cause the end S4 thereof to abut the .bolt edge `55 thereby to lift the latch bolt 16 upwardly against the resistance of the spring 46.

In the illustrated embodiment `of the invention the release lever means 2G is constructed and arranged so that parts thereof may be disassociated to render the outer manually operable means, such as the push button 26, ineffective to cause upward movement of the latch bolt 16. As stated earlier, the upper end of the arm 36 of the multiarmed member 33 normally lies in abutting relationship to the lower end of the bell crank lever arm 41. Thus, to Irender the push button 26 ineffective to cause latch bolt 16 movement, it is necessary to displace the multi-armed member 33 so as to position the upper end of its arm 36 out of abutting relationship to the bell crank arm 41. Since the multi-armed member 33 has been described as being Vpivotally mounted on the lever 21, the displacement thereof to despoil the abutting relationship of the bell crank arm 41 and the member arm 36 is accomplished by swinging the multi-armed member from the position shown in Fig. 1 to the position shown in Fig. 5.

In the embodiment of the invention as herein illustrated, the multi-armed member 33 may be shifted from its position as shown in Fig. l to its position as shown in Fig. 5 from either the outside or the inside of the vehicle door. From the outside of the vehicle door shiftable movement of the multi-armed member is actuated by turning a key in a conventional key cylinder locking mechanism (not shown). The key cylinder mechanism operates a control means, generally designated 56. The control vmeans includes `a lever 57 pivotally mounted on the case plate ange 12 on a pivot stud 58. The lever 57 is provided with two bifurcated portions. The upper bifurcated portion 59 operatively embraces the free end 60 of the arm 37 of the multi-arm member 33. The end 60 of the arm 37 is freely movable transversely of the bifurcated portion 59 of the lever 57 but lis loosely restrained against up and down movement relative thereto. The lower bifurcated portion 61 of the lever 57 is operatively engaged between the prongs 61a and 61b thereof by an upstanding lug 62 on the end of a swingable crank arm 63. The crank arm 63 is pivoted at 64 to the case plate flange 12 and is provided with a substantially rectangular opening 65 at the locality of its pivot to receive the key actuated shaft of the conventional cylinder locking mechanism having the usual key control. By turning the key in the locking mechanism from the outside of the vehicle door the crank arm 63 may be shifted in one direction or the other thereby causing swinging movement of the lever 57. For example, with reference to Fig. 2, if the crank arm 63 is swung in a counterclock- Wise direction the lever 57 will be swung in a clockwise direction thereby causing the multi-arm lever 33 to be swung downwardly from the position shown in Fig. 1 to the position shown in Fig. 5. As explained earlier, when the multi-arm lever 33 is in the position 'shown in Fig. 5, inward movement of the push butt-on 26 is .ineffective to raise the bollt 16 since the upper end of the multiarm lever arm 36 merely bypasses beneath the lower end of the bell crank lever arm 41. Thus, the latch mechanisrn is considered in locked condition.

Conversely, if the latch mechanism is in locked condition, proper turning of the key in the cylinder locking mechanism will cause the crank arm 63 to be swung in a clockwise direction, as viewed in Fig. 2, thereby swinging the lever 57 upwardly causing the multi-arm lever 33 to be swung upwardly to position its arm 36 in operative association with the arm 41 of the lever 38. The space between the two prongs 61a and 61b is substantially greater than the width of the crank arm lug 62 thus providing suicient lost motion so that the key, after lhaving been used to shift the lever 57 in one directionor the other, may be returned to a normal position in the key cylinder and retracted therefrom.

The #lever 57 may be Apivotally moved upwardly and downwardly from the inside of the vehicle door by means of a vertically shiftable rod or plunger 66. The lever 57 is provided with a small flange 67 lanced out of the face thereof into which the lower end 68 of the rod 66 is pivotally hooked. The vertically shiftable rod or plunger 66 is adapted to extend upwardly through the garnish molding at the inner side of the glass panel of the vehicle door. The rod 66 carries at its upper end a knob 69 which may be grasped at the inside of the door to shift the plunger vertically in either direction thereby rocking the lever '7 about its pivotal axis and causing the arm 36 of the lever 33 to be positioned in or out 0f abutting relation to the lever arm 41.

The lever 57 is yieldingly held and urged toward its upper and lower limits of movement by means of a snapover spring 70 of suitable strength attached at one end to the lever and at its opposite end to the case plate ilauge 12. The lower limit of movement is determined by a stop 'lug 71 lanced out of the case plate 10, the lug underlying the lower edge of the multi-arm lever arm 37. The upper limit of movement is determined by a stop lug 72 lanced out of the case plate ange 12 and overlying the upper edge of the lever 57.

The latch bolt 16 is provided with a horizontally extending pin 73 at the lower left han'd corner thereof as viewed in Fig. l. The pin 73, which may be integrally molded on the latch bolt or may be an insert thereon, extends through an elongated slot 74 in the case plate 1li. The pin 73 normally underlies the lower end of an angular extension 75 of the arm 35 of the multi-arm member 33. The relationship of the pin 73 and the extension 75 provides a means for automatically restoring the parts of the release means 20 into operative association under certain conditions. Referring to Fig. 5, when the multi-arm member 33 has been swung downwardly to drop the upper end of the arm 36 thereof below the lower end of the lever arm 41, the extension 75 of the arm 35 is substantially in abutting relation to the pin 73. Upon movement of the latch bolt 16 in an upward direction, the pin 73 will abut the arm extension 75 causing both the multi-arm member 33 and the control means 56 interlocked therewith to be swung upwardly to their normal operative positions as shown in Figs. 1 and 2. Even though the outside operator 26 may have been rendered ineiective to cause upward movement of the latch bolt 16, movement of the latch bolt 16 independently, of said outside operator may always be effected by actuation of the door handle on the inside of the door or by engagement of the latch bolt with the striker or keeper device as the door is swung from an opened to a closed position.

The foregoing construction has two advantages. The first advantage is that the occupants of the vehicle cannot be locked inside since actuation of the inside remote control handle will cause the bell crank 52 to be swung upwardly thereby raising the latch bolt 16. The pin 73 will abut the arm extension 75 thereby restoring the multi-arm lever 33 into operative association with the lever 38.

A further advantage is that in the event the latch mechanism is placed in locked condition when the door is open, and the door is then shut, the latch mechanism will automatically be restored to unlocked condition upon the latch bolt 16 engaging the striker or keeper device. It will be noted that the latch bolt projection 18 has an inclined leading edge 18a which upon engagement with the striker or keeper device 19 as the vehicle door is moved from an open to a shut position acts to cam the latch bolt upwardly. Since the lever roller 42 lies below the edge 45 and the bell crank arm extension 54 lies below the edge 55 of the latch bolt 16, upward movement of the latch bolt 16 upon engagement thereof with the striker or keeper 19 is independent of and does not result in any movement of the lever 38 or the bell crank 49. This independent movement of the latch bolt 16, through the abutting relation of the pin 73 to the -6 arm extension 75, if the multi-arm member 33 is in the position shown in Fig. 5, will automatically cause the multi-arm member 33 to be restored to the position shown in Fig. 1.

'Ihe illustrated embodiment of the invention has provision for preventing the aforementioned automatic restoration of the multi-arm member 33 from taking place. With reference to Fig. 6, it will be noted that if the multi-arm member 33 is in the down position and the push button 26 is held inwardly, the arm extension 75 is out of abutting relation to the pin 73. It will thus be apparent that if the latch mechanism is placed in locked condition, that is, with the multi-arm member 33 in the down position so that the arm 36 thereon is out of abutting relation to the lever arm 41, and the push button 26 is held inwardly, the end of the arm extension 75 will be out of the path of movement of the pin 73. Thus, if the vehicle door is moved from an open to a shut position with the push button 26 held inwardly, the resultant upward movement of the latch bolt 16 upon engagement with the striker or keeper device 19 will be ineifective to restore the latch mechanism parts to unlatched condition. However, since the act of holding the push button 26 inwardly is a deliberate one, it is believed that such act should be suiiicient reminder to prevent the door key from being inadvertently locked within the vehicle.

It will be readily apparent that if it is desired that the mechanism should always be restored to unlocked condition regardless of whether or not the push button 26 is held inwardly, it is only necessary to have the end portion 75 of the arm 35 of sufficient width so that it will always have a portion thereof lying in the path of the pin 73.

Fig. 7 illustrates the cooperative relationship between the latch bolt 16 and the keeper or striker device, hereinbefore generally designated 19, to hold the vehicle door in latched position. In general, the keeper or striker 19 comprises a C-shaped structure having upper and lower body portions 76 and 77 respectively. The upper body portion 76 is formed at its upper edge with two integral upstanding toothlike projections 78 and 79 which the latch bolt projection 18 is adapted to engage to hold the door in either safety or final Ilocking position. When the projection 18 is in engagement with the keeper tooth 78 the door is in safety latching position and when the projection 18 is in engagement with the tooth 79 the door is in final latching position.

The upper surface 80 of the lower body portion 77 forms a ramp engageable by a suitably contoured dovetail or abutment 81 fastened to the front face of the case plate 10. A yielrdable wedging means is carried on the underside of the upper body portion 76 of the striker device and engages the upper surface of the dovetail or abutment 81 to firmly hold the door against vibratory movement in a vertical plane. The wedging means in the present instance comprises a wedge block 82 controlled by a compression spring 83, the wedge block and spring being slidably retained within a recess 84 in the lower surface of the upper body portion 76 by means of a guide rod 85 fastened to the end walls of the recess 84. The spring 83 is installed under initial compression and urges the wedge outwardly or to the right as viewed in Fig. 7. During closing movement of the door, the wedge block 82 is carried inwardly to some extent against the resistance of the spring 83, the wedge block tending to tighten itself against the upper surface of the abutment 81 and hence maintaining the latch bolt projection 18 in engagement with the striker or keeper tooth 79 and also minimizing any possible vibratory movement of the vehicle door.

It will be noted that, although a compression spring 46 is provided to urge the latch bolt 16 downwardly into latching engagement with the striker or keeper 19,

. the` latch bolt 16. being,movable in a substantially up and 7 down direction will normally tend to maintain itself in latching .engagement with the striker or keeper.V Thus, even yif the spring 46 should ultimately fail, the vehicle 'door may still be latched so as to be maintained in a closed position until repairs can be made. This will, of course, be recognized as being an important feature from a safety standpoint.

The foregoing construction provides a lock mechanism having so-called free oating push button operation. That is, when the mechanism .is in locked condition thepush button.26 is freely movable without causing any movement of thelatch bolt. Thus, any :attempt to jump the mechanism from locked to unlocked vcondition by tapping the push button 26 with .a hammer will be obviously ineffective.

I claim:

1. `In a latch mechanism for a swinging door, a support having aplate portion adapted to be mounted on the free edge wall of the door and provided at its inner edge with a flange portion, a latch device slidably mounted on said plate portion for movement in a substantially up Vand down direction, lever means pivotally mounted on said plate portion swingable .to .raise said latch device, outer manually operable means mounted on .said plate portion, link means mounted for swinging movement, operable by said outer manually operable means upon movement of the same in a direction substantially parallel to said plate portion, and normally operatively coupled to said lever means, and inner manually operable means on said ange portion for swinging said link means into and out of coupled relation with said lever means.

2. In a latch mechanism for a swinging door, asupport having a plate portion adapted to be mounted on the free edge wall of the door and provided at its inner edge with a ange portion, a ,latch device slidably mounted on said plate portion for movement in' a substantially up and down direction, a iirsty lever pivotally mounted on said plate portion swingable to raise said latch device, a second lever pivotally mounted on said plate portion` and having la part swingable toward said ange portion upon actuation or" said lever from the outside of the door, link means pivoted to said second vlever and .having a part normally arranged in opposing relation to .a part vof said iirst lever and being shiftable transversely of the door to cause said parts to abut and .raise the latch device, and inner manually operable means for moving said linkzmeans to move said parts out of opposing relation.

3. ln a latch mechanism for a .swinging door, a support having a plateportion adapted to be mounted on .the tree edge wall of the door and provided at its inner edge with a ange portion, a latch device slidably mounted on said plate portion for movement in a substantially up and down direction, `a first lever pivotally mounted on said plate portion swingable to raise said latch device, Va second lever pivotally mounted on said Lplate portion 'and having a part swingable toward said ange portionupon actuation of said lever from the outside of .the door, link means pivoted to said .second lever and having a part normally arranged in opposing relation to a part of .said iirst lever and being shiftable to cause Asaid parts to abut and raise the latch device, control means swin-gably mounted on said support and having a substantially .up and down movable interlocking connection with one end of said link means, manually operable means for moving said control means to shift said link means to position its said part out of operative relation to said first lever part, and a .manually operable lever pivotally mounted on said support and engageable with said latch device and operative to etiect upward movement oisaid latch device 'and simultaneous shiftable movement of said .link means and control means to restore said parts in operative relation.

4. In a door latch mechanism for a swinging door, a support having a plate portion for disposition `at the lfree edge wall of the door, a Yvertically slidable latch bolt means mounted `on the outer side of .said plateportion and having a striker engaging portion at the lower end thereof, outer -manually operable means movable transversely of the door, actuator means responsive to movement of said outer manually operable means effective to raise said bolt means out of striker engagement, said actuator means including at least two members pivotally mounted on said plate portion, one of said members having a part thereof in engagement with said bolt means, the other of said members being selectively movable into and out of operative relationship to said one member thereby rendering said actuator means selectively operative or inoperative to transmit movement of said outer manually operable means to said vbolt means, and control means effective to move said other member into and out of such operative relationship.

5. In a door latch mechanism for a swinging door, a support having a plate portion for disposition at the free edge wall of the door, a vertically slidable 'latch bolt means .mounted on the outer side of said plate portion and having'a striker engaging portion at the lower end thereof, outer manually operable means movable transversely of the door, actuator means responsive to movement of said outer manually operable means eiective to raise said bolt means out of striker engagement, said actuator means including at least two members pivotally mounted on said plate portion, one of said members having a part thereof in engagement with said bolt means, the other of said members being selectively movable into and out of operative relationship to said one member thereby rendering said a-ctuator means selectively operative or inoperative to transmit movement of said outer manually operable means to said bolt means, and control means elective to move said other member into and out of such operative relationship with said one member having a part normally engageablc by a part of said latch bolt means upon upward movement thereof effective to restore such operative relationship, said other member being selectively positionable to move its said part out of the path of said latch bolt means part thereby preventing restoration of said operative relationship.

6. In a door latch mechanism for a swinging door, a support having a plate portion for disposition at the free edge wall of the door, a vertically slidable latch bolt means mounted on the outer side of said plate portion and having a striker engaging portion at the lower end thereof, outer manually operable means movable transversely of the door, actuator means responsive to movement of said outer manually operable means effective to raise said bolt means out of striker engagement, said actuator means including at least two members pivotally mounted on said plate portion, one of said members having a part thereon projecting through an aperture in said plate portion and arranged in opposing relation to a part of said bolt means, the other of said members being selectively movable into and out of operative relationship to said one vmember thereby rendering said actuator means selectively operative or inoperative to transmit movement of said outer manually operable means to said bolt means, and control means effective to move said other member into and out of such operative relationship, said other member when out of operative relationship with said one member having a part thereof normally engageable by a part of said latch bolt means upon upward movement thereof effective to restore such operative relationship.

References Cited in the tile of this patent UNITED STATES PATENTS 2,039,873 Andersen et al. May 5, 1936 2,234,810 Simpson Mar. l1, 1941 '2,236,702 Andersen Apr. l, 1941 2,569,042 Endter Sept. 25, 1951 2,683,617 Roethel luly 13, 1954 2,736,591 Roethel Feb. 28, 1956 

